the unerupted maxillary canine Flashcards
what is the prevalence of ectopic canines?
> 2% of the population
> palatally = 61%
line of arch = 34%
buccal = 4.5%
what is the ratio of unilateral to bilateral ectopic canines?
> 4 : 1
is ectopic canines more common in females than males ?
> females (70%)
when are ectopic canines more likely to occur?
> when a patient has a class II div 2 malocclusion
what is the primary problem of ectopic canines?
> it can cause root absorption of the adjacent tooth
what tooth is most likely to be affected by root resorption by an ectopic canine?
> lateral incisor
> but can be multiple teeth (if lateral is missing, central is at risk)
what is the best methods in measuring root resorption?
- CBCT
- CT
- plane R/G (as 2D unable to fully show palatal resorption)
why does an ectopic canine happen ?
> Crowding/shortening of arch length (common for buccal) (Jacoby, 1983)
> Adjacent lateral incisor missing or abnormal in shape or size
> Long path of eruption (Brin et al., 1986)
> Palatal = genetic; buccal = inadequate arch space
what did the Brin et al study find on ectopic canines?
> 43 % of test subjects had absent or small incisors
> length of the root more critical than crown size as the root guides the canine into position
what should you do if the canine is not palpable buccally at 9-10 years?
- Check – bulge, inclination and colour of adjacent teeth.
- Palpate – for the canine crown buccally and palatally, check for mobility of the 2 and C.
- Radiographs – Presence, Position, Pathology (root resorption/ cyst formation)
what is parallax radiograph technique?
> an apparent change in the position of an object resulting from a change in position of the observer.
> The principle of parallax can be used to determine the position of an unerupted tooth relative to its neighbours.
when do we use the parallax technique?
> Dentists should be palpating for canines when a patient is 9-10 years old.
> Index of suspicion is raised if the pt has a missing, or abnormally shaped lateral incisor; has spaced arches, or if palpation indicates an asymmetrical eruption pattern
what are the clinical signs of a palatally impacted canine?
> Delayed eruption of 3 or prolonged retention of the C
> Absence of normal labial 3 bulge or presence of a palatal bulge in the 3 region.
> Delayed eruption, distal tipping of migration of the lateral incisor.
> Loss of vitality and increased mobility of the central or lateral incisor
why do we use the parallax technique?
> Knowing the location of the ectopic canine allows us to treatment plan more accurately.
> If not managed correctly an ectopic canine may resorb the root of the adjacent incisors. This may result in a medico-legal encounter.
how do we take horizontal parallax?
> two IOPAs - at least 20 degrees of tube shift needed
> Anterior occlusal and an IOPA
how do we take vertical parallax
> anterior occlusal and DPT
> IOPA and DPT
how do you interpret parallax?
> if the canine moves with the beam its placed palatally , (the furthest away object will move with the beam) (with it pal)
> if it doesn’t move its in the line of arch
what is better to use, horizontal or vertical parallax?
> In a study of 39 patients Armstrong et al. 2003 found that 69% of palatal ectopic canines were correctly located with VP, compared to 88% with HP.
> Both came back with 63% accuracy for buccal ectopic canines.
> The paper suggested that DPTs shouldn’t be used in the investigation of canine ectopia, where radiographs that allow the use of HP should be taken.
what did the Ericsson & Karol study find out about ectopic canines?
> non crowded dentition
> extraction of deciduous canines yielded a 78% of self correcting an ectopic canine
> however If the lateral incisor root is in the way this greatly decreases the chance of self correction
what did the power and short study find out about ectopic canines?
> crowded dentition
> removal of the deciduous canine yielded = 62% self corrected, 19% improved, 19% no change
> crowding reduced the dentition
what did the Leonard et al find out about ectopic study?
> Longitudinal prospective controlled study
> Isolated extraction of C = 50% success
> Untreated control group = 50% success
> Creation of more space + extraction of C = 80% success
when would you extract a deciduous canine in a patient?
> 10-13 years
what do you have to consider when extracting a deciduous canine?
> consider the need for a balancing extraction
> it is better if there is no crowding
> consider the use of an URA or headgear to create space
> if no improvement in 12 months then other options should be considered
why would you leave the decision of extraction of a deciduous canine to a specialist orthodontist?
> this will often be the treatment of choice
> however, ectopic canine may not be align-able and you may have extracted a highly useful tooth
> you’ll be left with a space if done wrong, always make a referral
what patients are suitable for surgical exposure and orthodontic alignment?
> Willing to wear fixed appliances (good oral health)
> Well motivated and have good dental health
> Unsuitable for interceptive treatment
> Degree of malposition not too great
what do you consider when judging the degree of malposition?
> apex position - how far is it from where you’d expect it to be?
> crown position - is the crown beyond the midline of the lateral incisor, is it beyond the of the central incisor or even has it regressed beyond the midline??
> angulation - the more inclined the longer the time
> the more malposition the tooth is the longer treatment will last and the less likely there will be success
what are the 2 types of surgical exposure?
> open exposure
> closed exposure
what is open exposure?
> overlying mucosa removed to expose the tooth,
> tooth can then be bonded to appliances
> (advantage is that the orthodontist can visualise better)
what is a closed exposure?
> tooth is uncovered and a gold chain is attached, then the mucosa is put back in place. the gold chain is then attached to the orthodontic appliance and the forces pull the tooth threw.
> (you cannot see the canine)
> tends to be used when the tooth is farther away from the surface or an if an open exposure could cause damage to gingival tissue are adjacent teeth
what is the impact on periodontal health between the open eruption and closed eruption? (Parkin et al)
> no evidence either method is superior
what is the cost analysis of interceptive treatment in treatment of ectopic canines?
> only extraction of decidous canine
what is the cost analysis of surgical exposure in the treatment of ectopic canines?
> Oral surgeon
> General anaesthetic
> 18 months of fixed appliance treatment
what are the treatment options for an ectopic canine?
- No treatment and observe long term for cystic change (cysts can absorb other teeth, after later teens this risk is reduced)
- Interceptive treatment where appropriate
- Exposure and alignment
- Extraction
- Transalveolar transplant or surgical repositioning
what are the orthodontic treatment risk in ectopic canines?
> Risk of root resorption to adjacent teeth (lateral incisor and first premolar)
> Risk of pulpal obliteration to canine and adjacent teeth causing colour mismatch
> Risk of discontinued treatment due to prolonged treatment times
> Canine ankylosis, if other teeth move towards the canine in treatment this would suggest the canine is ankylosed
> High tendency to relapse
what should you do if you identify an ectopic canine clinically or radiographically?
> Where canine ectopia is identified clinically or radiographically an urgent referral with copies of relevant radiographs should be sent to an orthodontic specialist
